Extract command UX improvements: dry-run, include-global, detection summary #88

Context

PR #87 added --tool, --component, --scope filters to devsync extract. The filtering works, but the UX has gaps.

Changes

• --dry-run flag: Show detected components without writing files or calling the LLM
• Detection summary table: Display what was found before the slow LLM step
• Zero-result warning: Helpful message with suggestions when filters match nothing
• Enhanced output: Per-tool breakdown replacing minimal counts
• --include-global flag: Replaces confusing three-way --scope option (deprecated with warning)
• devsync tools --verbose: Show capabilities column and valid --component filter names
• Updated docs: docs/cli/extract.md reflects new flags

Acceptance Criteria

• devsync extract --dry-run shows detection table, no files written
• devsync extract --dry-run --tool cursor filters to cursor only
• devsync extract --dry-run --component hooks --tool cursor with zero result shows suggestions
• devsync extract --include-global includes home directory configs
• devsync extract --scope all shows deprecation warning, still works
• devsync tools -v shows capabilities column
• All tests pass